Maglev Rotor Position Control for Stable CT Scanner Levitation
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Solution Overview
Problem
Existing CT apparatuses face challenges in achieving stable rotor levitation due to attractive forces between the stator and rotor, leading to vibrations and potential contact, which can cause wear and hinder miniaturization.
Innovation Solution
A rotation drive apparatus with a rotor and stator configuration that includes circumferentially arranged permanent magnets and coils, controlled by a current control system to maintain levitation by adjusting the rotor's position based on detected displacement and torque, ensuring stable levitation and reduced cogging torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnets and coils with cores are used in the synchronous motor to achieve high torque, then torque is improved, but attractive force is always generated between the stator and rotor causing vibration and instability during levitation
Solution Approach 1:
The control unit rotates the rotor to a predetermined position before initiating levitation. This preliminary action ensures that the rotor starts from a position with minimal attractive force, preventing vibration and instability during the transition to levitation state
Solution Approach 2:
The control unit continuously monitors the levitation force and adjusts the current to the coils accordingly. By detecting when levitation force reaches a predetermined value, the system provides feedback control to maintain stable levitation while managing attractive forces
2Speed
If the rotor is levitated from a seated state supported by magnetic bearing, then levitation is achieved, but attractive force pulls the rotor in a direction different from gravity causing vibration and potential contact
Solution Approach 1:
Before levitation is initiated, the control unit rotates the rotor to a predetermined position where attractive force is minimized. This preliminary positioning prevents the rotor from vibrating and contacting the magnetic bearing during the levitation transition
Solution Approach 2:
The system applies a counteracting rotational action to offset the harmful attractive force. By rotating the rotor to a specific position before levitation, the attractive force that would otherwise cause vibration and instability is preemptively counteracted
3Reliability
If the rotor vibrates during levitation transition, then levitation is achieved, but the rotor or magnetic bearing may wear out due to contact
Solution Approach 1:
The control unit rotates the rotor to a predetermined position before levitation begins, ensuring that the rotor starts from a stable position with minimal attractive force. This prevents vibration and contact with the magnetic bearing, extending its lifespan
Solution Approach 2:
The system preemptively positions the rotor to avoid harmful vibrations and contact. By establishing a favorable starting position before levitation, the magnetic bearing is protected from wear and damage
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables stable rotor levitation without enlarging the apparatus, reducing vibrations and wear, facilitating miniaturization and improved positional accuracy in CT scanners.
Implementation Method 1
a magnetic force unit that includes a stator and a rotor... rotating the rotor... by the action of magnetism
Implementation Method 2
a magnetic levitation motor using a magnetic bearing... rotor is rotated in a contactless state by the action of magnetism
Implementation Method 3
an attractive force is always generated between the stator and the rotor... pulls the rotor in a direction different from the direction of gravity
Data Source
AI summary
A rotation drive apparatus includes: a rotor that includes a first magnetic force unit and is rotatable in a rotation direction around a rotation axis intersecting a direction of gravity; a stator that includes a second magnetic force unit; a support that supports the rotor positioned in a first position; and a control unit, wherein the first magnetic force unit is arranged circumferentially along the rotation direction on an outer peripheral side surface of the rotor, the second magnetic force unit is arranged in an arc shape along the rotation direction above the rotor, and, when the rotor is positioned at the first position and a levitation force with respect to the rotor is less than a predetermined value, the control unit rotates the rotor to a second position where the levitation force is equal to or greater than the predetermined value and levitates the rotor from the second position.